Display systems, such as liquid crystal display (LCD) systems, have been implemented using a central processing unit (CPU), a display image buffer, and a display driver driving a display panel. For large screen LCD displays, the CPU operates to copy data from the display image buffer and apply the data to the display driver in a pixel-by-pixel manner. The driver produces a voltage on the display panel that controls the pixels thereon to have a particular intensity and decay rate. The process of applying a voltage is done repeatedly, at timed intervals, and is known in the art as "refreshing the display."
Display systems for small panels require a proportionally smaller display image buffer than systems for larger display panels. Many systems for small display panels implement the display image buffer in the same integrated circuit (IC) as the logic circuitry for controlling the display panel, such buffer known as an internal buffer. This approach yields a much lower current drain than using an external memory device for the display image buffer. However, the size of the display panel that can be driven by the integrated buffer is limited by the die area available for the display image buffer on the IC. Another drawback with this approach is CPU access to the internal display image buffer is restricted. Because access is restricted, as the display gets bigger the CPU has a more difficult time changing the contents of the internal display image buffer fast enough to avoid flicker and hesitation during scrolling. Consequently, for display systems employing an internal buffer for a large display panel, it is difficult to scroll images on the display panel in a smooth consistent manner.
It is therefor desirable to provide a system for controlling a large display with improved current drain characteristics.